Aerosol containers or cans for a variety of active components are charged with propellant. Usually, a plurality of filling lines is provided to charge the cans with one of a number of possible propellant compositions.
It is often necessary to change over from a feed of one propellant to feed of another propellant as the active component changes in the containers to be charged. When such a changeover is made, there is inevitably a quantity of the first propellant present in the feed line. Conventionally, this residual amount of first propellant is vented to atmosphere.
With increasingly-stringent restrictions on atmospheric emissions, increasing pressure has arisen to avoid venting propellant. The aim of the present invention is to avoid such venting while, at the same time, retaining an efficient propellant filling operation.